Benefits of extended sous vide time?

My roommate made some short ribs from a recipe that called for a 48-hour cooking time at like 144F. They were indeed delicious, but I'm trying to figure out why that extended cooking time is necessary, and why it is better than a 12- or 24-hr cooking time, both of which the recipe writers said produced inferior results. (They actually said 72 hours produced the best results, but I guess 48-hrs is a compromise?). Is it just an extended maillard reaction, or is some other physical change happening? Or do you think a double-blinded testing would have yielded different results. FYI, the meat had been marinated, but I think went into the bag without any additional liquid. Also, the 24-hr …